Cha宏观经济学曼昆

8SHORT-RUN

ECONOMICFLUCTUATIONS短期经济波动20Aggregate

Demand

andAggregate

Supply总需求与总供给本章我们将探索这些问题的答案：什么是经济波动？它们的特点是什么？总需求与总供给模型如何解释经济波动？为什么总需求曲线向右下方倾斜？什么使总需求曲线移动？短期总供给曲线的斜率是多少？长期的呢？什么使总供给曲线移动？3Short-Run

EconomicFluctuationsEconomic

activity

fluctuates

from

year

toyear.In

most

years

production

of

goods

andservices

rises.On

average

over

the

past

50

years,production

in

the

U.S.

economy

has

grownby

about

3

percent

per

year.In

some

years

normal

growth

does

not

occur,causing

a

recession.短期经济波动经济活动每年都有波动。在大多数年份，物品与劳务的产量增加了。在过去的50年间，美国经济的产量平均每年增长3%左右。在一些年份，并没有出现这种正常增长，导致衰退。Short-RunEconomic

Fluctuations短期经济波动A

recession

is

a

period

of

decliningreal

incomes,

and

risingunemployment.衰退——实际GDP下降和失业增加的时期。A

depression

is

a

severe

recession.萧条——严重的衰退。20.1

THREE

KEY

FACTS

ABOUTECONOMIC

FLUCTUATIONS(1)Economic

fluctuations

are

irregular

andunpredictable.–

Fluctuations

in

the

economy

are

often

calledthe

business

cycle.(2)Most

macroeconomic

variablesfluctuate

together.(3)As

output

falls,

unemployment

rises.20.1

关于经济波动的三个事实(1)经济波动是无规律的和无法预测的。经济中的波动通常被称为经济周期。(2)大多数宏观经济变量同时波动。(3)随着产量减少，失业增加。Figure

1

A

Look

AtShort-Run

EconomicFluctuationsReal

GDP(a)

Real

GDPBillions

of1996

Dollars$10,0009,0008,0007,0006,0005,0004,0003,0002,0001965

1970

1975

1980

1985

1990

1995

2000图1.观察短期经济波动Real

GDP(a)实际GDP1996的10亿美元$10,0009,0008,0007,0006,0005,0004,0003,0002,0001965

1970

1975

1980

1985

1990

1995

2000Most

macroeconomic

variables

fluctuatetogether

大多数宏观经济变量一起波动.Most

macroeconomic

variables

that

measuresome

type

of

income

or

production

fluctuateclosely

together

大多数衡量某种收入或产出的宏观经济变量同时波动.Although

many

macroeconomic

variablesfluctuate

together,they

fluctuate

by

differentamounts

尽管很多宏观经济变量一起波动，但是它们波动的大小并不同.Figure

1

A

Look

AtShort-Run

EconomicFluctuations(b)

Investment

SpendingBillions

of1996

Dollars$1,8001,6001,4001,2001,0008006004002001965

1970

1975

1980

1985

1990

1995

2000Investment

spending图1.观察短期经济波动(b)投资支出1,4001,2001,0008006004002001965

1970

1975

1980

1985

1990

1995

2000Investment

spending1996的10亿美元$1,8001,600As

output

falls,unemployment

rises随着产量减少，失业增加.Changes

in

real

GDP

are

inversely

relatedto

changes

in

the

unemploymentrate

实际

GDP的变化与失业率的变化是反向相关的.During

times

of

recession,unemploymentrises

substantially

在衰退期间，失业率大幅上升.Figure

1

A

Look

AtShort-Run

EconomicFluctuations(c)

Unemployment

Rate06428Percent

ofLabor

Force12101965

1970

1975

1980

1985

1990

1995

2000Unemployment

rateCopyright

©

2004

South-Western图1.告步观察亲短期纺经济练波动(c)失业蒜率06428劳动力惩的百分比驱1210196错5197殃0197趋5198苗0198束5199鞠0199藏5200谦0Unemploymentr立a芽te锡20.2EXPLAININGSHORT-RUNECONO速MICFLUCTUATIONS(1)HowtheShortRunDiffersfromtheLongRunMosteconomistsbelievethatclassicaltheorydescribestheworldinthelongrunbutnotintheshortrun.Changesinthemoneysupplyaffectnominalvariablesbutnotrealvariablesinthelongrun.Theassumptionofmonetaryneutralityisnotappropriatewhenstudyingyear-to-yearchangesintheeconomy.20.2解释短期经济波动(1)长期与短期有什么不同大多数经济学家认为，古典经济理论描述长期世界，并不描述短期世界。在长期中，货币供给的变化影响名义变量，而不影响实际变量。在研究逐年的经济变动时，货币中性的假设就不再适用了。TheBasicModelofEconomicFluctuations(2)Twovariablesareusedtodevelopamodeltoanalyzetheshort-runfluctuations.Theeconomy’soutputofgoodsandservicesmeasuredbyrealGDP.TheoverallpricelevelmeasuredbytheCPIortheGDPdeflator.经济波动的基本模型(2)两个变量被用来建立模型分析短期经济波动。用实际GDP衡量的经济中的物品与劳务的产量。用CPI或GDP平减指数衡量的物价总水平。(3)TheBasicModelofEconomicFluctuations经济波动的基本模型TheBasicModelofAggregateDemandandAggregateSupply总需求与总供给基本模型–

Economistusethemodelofaggregatedemandandaggregatesupplytoexplainshort-runfluctuationsineconomicactivityarounditslong-runtrend.经济学家用总需求与总供给模型来解释经济活动围绕其长期趋势的短期波动的模型。Theaggregate-demandcurveshowsthequantityofgoodsandservicesthathouseholds,firms,andthegovernmentwanttobuyateachpricelevel.总需求曲线——一条表示在每一种物价水平时家庭、企业和政府想要购买的物品与劳务量的曲线。Theaggregate-supplycurveshowsthequantityofgoodsandservicesthatfirmschoosetoproduceandsellateachpricelevel.总供给曲线——一条表示在每一种物价水平下企业选择生产并销售的物品与劳务量的曲线。Fi趁gur施e2奖A引牌ggr浓e炊gat扩eD烧萝em漠and挖虎and翅A烈gg吗r腿ega胜te逐S常u洒ppl行y...棵Qua猫nt屠it燥yo祝f沿Out提pu开tPri宽ce煎Le迟vel氏0AggregatesupplyAggregatedemandEquilibriumoutputEquilibriumprice

level图2.挪没总需塌求与痕总供凝给牙…产量物价水平0总供给总需求均衡产量均衡物价水平20.3TheAggregateDemandCurve总需求曲线ThefourcomponentsofGDP(Y)contributetotheaggregatedemandforgoodsandservices.GDP(Y)的四个组成部分对物品与劳务的总需求做贡献。Y=C+I+G+NXFi拳gur颈e3仗T没覆heA研乘ggr雪e幕gat但e出-D尿em曲and菠酷Cur助ve的..过.Qua标nt勿it颈yo悔f界Out投pu甚tPri愈ce蜓Lev岂el化0AggregatedemandPY

Y2P21.

A

decreasein

thepricelevel

.

.

.2.

.

.

.

increases

the

quantity

ofgoods

and

services

demanded.图3.撞怕总需敏求曲草线…产量物价水平0总需求PY

Y2P21.物价水平下降...2.…物品与劳务量增加20.3.1WhytheAggregate-DemandCurveIsDownw侧ardSloping为什么总需求曲线向右下方倾斜（1）ThePriceLevelandConsumption——TheWealthEffect物价水平与消费——财富效应（2）ThePriceLevelandInvestment——TheInterestRateEffect物价水平与投资——利率效应（3）ThePriceLevelandNetExports——TheExchange-RateEffect物价水平与净出口——汇率效应（1）ThePriceLevelandConsumpt乡丰ion:TheWealthEffect物价水平与消费:财富效应Adecreaseinthepricelevelmakesconsumersfeelmorewealthy,whichinturnencouragesthemtospendmore.物价水平下降使消费者感到更富裕，这又鼓励他们更多地支出。Thisincreaseinconsumerspendingmeanslargerquantitiesofgoodsandservicesdemanded.消费支出增加意味着物品与劳务的需求量更大了。（2）ThePriceLevelandInvestment:TheInterestRateEffect物价水平与投资:利率效应Alowerpricelevelreducestheinterestrate,whichencouragesgreaterspendingoninvestmentgoods.较低的物价水平降低了利率，鼓励了更多地支出用在投资物品上Thisincreaseininvestmentspendingmeansalargerquantityofgoodsandservicesdemanded.这种投资支出的增加意味着物品与劳务的需求量更大了（3）ThePriceLevelandNetExports:TheExchange-RateEffect物价水平与净出口：汇率效应WhenafallintheU.S.pricelevelcausesU.S.interestratestofall,therealexchangeratedepreciates,whichstimulatesU.S.netexports.当美国物价水平下降引起美国利率下降时，实际汇率贬值，而且这种贬值刺激了美国的净出口。Theincreaseinnetexportspendingmeansalargerquantityofgoodsandservicesdemanded.净出口开支的增加意味着物品与劳务的需求量更大了20.3.2WhytheAggregate-DemandCurveMightShiftThedownwardslopeoftheaggregatedemandcurveshowsthatafallinthepricelevelraisestheoverallquantityofgoodsandservicesdemanded.Manyotherfactors,however,affectthequantityofgoodsandservicesdemandedatanygivenpricelevel.Whenoneoftheseotherfactorschanges,theaggregatedemandcurveshifts.20.3.2为什么总需求曲线会移动总需求曲线向右下方倾斜表明物价水平下降增加了物品与劳务的总需求量。但是，许多其他因素也影响既定物价水平时的物品与劳务的需求量。当这些因素中的一种变动时，总需求曲线移动。Shiftsarisingfrom移动起因于Consumption消费Investment投资GovernmentPurchases政府购买NetExports净出口ShiftsintheAggregateDemandCurveQuantity

ofOutputPriceLevel0P1Y1D2Aggregatedemand,

D1Y2总需求曲线的移动产出物价水平0P1Y1D2总需求,D1Y2在下列各种情形中，总需求曲线会发生什么变动？A.一个十年期的投资税收优惠到期

B.美元汇率下降C.物价水平的下降增加了消费者财富的真实价值

D.州政府对利息，红利和资本收益征收新税以取代销售税课堂练习1总需求曲线37一个十年期的投资税收优惠到期投资减少，总需求曲线向左移动美元汇率下降净出口增加，总需求曲线向右移动物价水平的下降增加了消费者财富的真实价值沿总需求曲线移动（财富效应）州政府对利息，红利和资本收益征收新税以取 代销售税消费增加，总需求曲线向右移动38课堂练习1参考答案20.4THEAGGREGATE-SUPPLYCURVE总供给曲线Inthelongrun,theaggregate-supplycurveisvertical.在长期中，总供给曲线是垂直的。Intheshortrun,theaggregate-supplycurveisupwardsloping.在短期中，总供给曲线是向右上方倾斜的。TheLong-RunAggregate-SupplyCurveInthelongrun,aneconomy’sproductionofgoodsandservicesdependsonitssuppliesoflabor,capital,andnaturalresourcesandontheavailabletechnologyusedtoturnthesefactorsofproductionintogoodsandservices.Thepriceleveldoesnotaffectthesevariablesinthelongrun.20.4.1WhytheLong-Runaggregate-supplycurveisvertical.长期总供给曲线在长期中，一个经济的物品与劳务供给取

决于它的资本、劳动和自然资源的供给，以及用来把资本与劳动变为物品与劳务的生

产技术。在长期中，物价水平并不影响这些变量。20.4.1为什么长期总供给曲线是垂直的Fi行gur凑e4桃T填剩heL吼柔ong龄-钥Run饥A破gg走r绑ega棚te努-S宏u嚼ppl欧yC臣u害r稼veNat狼ur银al破r绒at招e

Qua鹿nt沸it遇yo屈f站ofo抢u填t福put磁

Out芦pu泛tPri充ce示Le括vel植0Long-runaggregatesupplyP21.

A

changein

thepricelevel

.

.

.2.

.

.

.does

not

affectthe

quantity

of

goodsand

servicessuppliedin

the

long

run.P图4.屿指长期贩总供舍给曲刘线产量自然喘产量雁率物价水平0长期总供给P21.物价水平变动…2...并不影响长期中物品与劳务的供給量PTheLong-RunAggregate-SupplyCurve长期总供给曲线Thelong-runaggregate-supplycurveisverticalatthenaturalrateofoutput.长期总供给曲线是在自然产量率时的一条垂线。Thislevelofproductionisalsoreferredtoaspotentialoutputorfull-employmentoutput.这一产量水平也被称为潜在产量或充分就业产量。20.4.2WhytheLong-RunAggregate-SupplyCur于veMightShift为什么长期总供给曲线会移动Anychangeintheeconomythataltersthenaturalrateofoutputshiftsthelong-runaggregate-supplycurve.经济中任何改变自然产量率的变动都会使长期总供给曲线移动。Theshiftsmaybecategorizedaccordingtothevariousfactorsintheclassicalmodelthataffectoutput.可以根据古典模型中影响产量的各种因素把这些移动进行归类。Shiftsarisingfrom移动起因于Labor劳动Capital资本NaturalResources自然资源TechnologicalKnowledge技术知识20.4.3ANewWaytoDepictLong-RunGrowthandInflation描述长期增长与通货膨胀的新方法Short-runfluctuationsinoutputandpricelevelshouldbeviewedasdeviationsfromthecontinuinglong-runtrends.应该把短期产量与物价水平波动作为与持续的长期趋势的背离。Fi极gur恭e5逢L询班ong喇-师Run处G腹r糖owt浮ha瞎辽ndI尘n山fl狭at类i镜onQu妹ant秃it良yo畏f骆Out赚pu维tY1980AggregateDemand,

AD2000AD19900AD1980Y1990

Y2000Long-runaggregatesupply,LRAS1980

LRAS1990LRAS2000P19801.

In

the

long

run,technologicalprogress

shiftslong-run

aggregatesupply

.

.

.4.

.

.

.

andongoing

inflation.3.

.

.

.

leading

togrowthin

output

.

.

.P1990P20002.

.

.

.

and

growth

in

themoney

supply

shiftsaggregate

demand

.

.

.Pr嗓ice己Le山ve掀l图5.心恭长绢期增挂长与郊通货聋膨胀产量Y1980AD1990总需求AD20000长期总供给LRAS1980

LRAS1990LRAS2000P19801.在长期中，技术进步使长期总供给移动….4.....及持续.的通货膨胀AD1980Y1990

Y20003.....引起产量增长….P1990P20002.....以及货币供给增长使总需求移动…物价水平20.4.4WhytheAggregate-SupplyCurveSl呆opesUpwardintheShortRun为什么短期中总供给曲线向右上方倾斜Intheshortrun,anincreaseintheoveralllevelofpricesintheeconomytendstoraisethequantityofgoodsandservicessupplied.在短期中,经济中物价总水平的上升倾向于增加物品与劳务的供給量。Adecreaseinthelevelofpricestendstoreducethequantityofgoodsandservicessupplied.物价总水平的下降倾向于减少物品与劳务的供給量。Fi过gur抛e6事T演访heS备赖hor谈t姨-R讯unA港雕ggr飘e母gat笑e-乖S周upp孝ly返震Cur诵v乎eQua乔nt陈it水yo科f西Out锯pu晃tPri巷ce库Lev天el捉0Short-runaggregatesupply1.

A

decreasein

thepricelevel

.

.

.2.

.

.

.

reduces

the

quantityof

goods

and

servicessupplied

in

the

short

run.YPY2P2图6.就只短期绩总供派给曲蛋线产量物价水平0短期总供给1.物价水平下降….2.

减少了短期中物品与劳务的供給量。YPY2P2WhytheAggregate-SupplyCurveSlopesUpwardintheShortRun为什么短期中总供给曲线向右上方倾斜TheMisperceptionsTheory错觉理论TheSticky-WageTheory粘性工资理论TheSticky-PriceTheory粘性价格理论（1）TheMisperceptionsTheoryChangesintheoverallpriceleveltemporarilymisleadsuppliersaboutwhatishappeninginthemarketsinwhichtheyselltheiroutput:Alowerpricelevelcausesmisperceptionsaboutrelativeprices.Thesemisperceptionsinducesupplierstodecreasethequantityofgoodsandservicessupplied.（1）错觉理论物价总水平的变动会暂时误导供给者对他们出售其产品的市场发生的变动的看法:低物价水平引起对相对价格的错觉。这些错觉引起供给者减少物品与劳务的供給量。（2）TheSticky-WageTheoryNominalwagesareslowtoadjust,orare“sticky”intheshortrun:Wagesdonotadjustimmediatelytoafallinthepricelevel.Alowerpricelevelmakesemploymentandproductionlessprofitable.Thisinducesfirmstoreducethequantityofgoodsandservicessupplied.（2）粘性工资理论名义工资调整缓慢，或者说在短期中是“粘性的”:工资不能根据物价水平迅速调整。较低的物价水平使就业和生产不利。这就引起企业减少物品与劳务的供給量。（3）TheSticky-PriceTheoryPricesofsomegoodsandservicesadjustsluggishlyinresponsetochangingeconomicconditions:Anunexpectedfallinthepricelevelleavessomefirmswithhigher-than-desiredprices.Thisdepressessales,whichinducesfirmstoreducethequantityofgoodsand（3）粘性价格理论一些物品与劳务的价格对经济状况变动的调整也是缓慢的:未预期到的物价水平下降使一些企业的价格高于合意水平。这就抑制了销售，并引起企业减少它们生产的物品与劳务量。20.4.5WhytheShort-RunAggregate-SupplyCurveMightShift为什么短期总供给曲线会移动Shiftsarisingfrom移动起因于Labor劳动Capital资本NaturalResources.自然资源Technology.技术ExpectedPriceLevel.预期物价水平Anincreaseintheexpectedpricelevelreducesthequantityofgoodsandservicessuppliedandshiftstheshort-runaggregatesupplycurvetotheleft.预期物价水平上升减少了物品与劳务供給量，并使短期总供给曲线向左移动。Adecreaseintheexpectedpricelevelraisesthequantityofgoodsandservicessuppliedandshiftstheshort-runaggregatesupplycurvetotheright.预期物价水平下降增加了物品与劳务供給量，并使短期总供给曲线向右移动。Fi稀gur嗓e7冶T构橡heL倾伸ong至-崇Run地E蛾qu记il单ib泄ri秆um色Natural

rateofoutputQua毙nt填it打yo蓝f摊Out弊pu苗tPri臂ce盆Le烈vel吨0Short-runaggregatesupplyLong-runaggregatesupplyAggregatedemandAEquilibriumprice图7.趣魂长期除均衡自然产量率产量物价水平0短期总供给长期总供给总需求A均衡价格20.5TWOCAUSESOFECONOMICFLUCTUATIONS（1）ShiftsinAggregateDemandIntheshortrun,shiftsinaggregatedemandcausefluctuationsintheeconomy’soutputofgoodsandservices.Inthelongrun,shiftsinaggregatedemandaffecttheoverallpricelevelbutdonotaffectoutput.20.5经济波动的两个原因（1）总需求移动在短期中，总需求移动引起经济中物品与劳务产量的波动。在长期中，总需求移动影响物价总水平，但不影响产量。Fi乞gur炭e8而A仰C开拍ont毛r遮act润i篮oni疾n牌A烘gg亦r晃ega躁te砖惨De惕ma萝ndQua珠nt玻it旺yo烘f避Out内pu牧tPri厅ce贵Lev腹el斜0Long-runaggregate敏supplyPYAggregatedemand,

ADAD21.

A

decrease

inaggregate

demand

.

.

.2.

.

.

.causes

output

to

fall

in

the

short

run

.

.

.Short-run

aggregatesupply,

ASAS23.

.

.

.but

overtime,

the

short-runA

aggregate-supplycurve

shifts

.

.

.4.

.

.

.

and

outputreturnsto

its

naturalrate.CP3BP2Y2图8.趣驰总需岩求减械少产量物价水平0长期总供给APY总需求,ADAD21.总需求减少…..2....引起短期中产量减少...短期总供给,AS1AS23……但随着时间推移，短期总供给曲线移动……4……产量恢复到其自然产量率水平。CP3BP2Y2画出美国经济的AD-SRAS-LRAS图形，从经济的长期均衡开始加拿大出现经济繁荣，用你的图形分析这对美国GDP，物价水平和失业率的短期与长期影响课堂练习2模型的应用68课堂练习2参考答案69LRASYNPYAD2SRAS2AD1SRAS14.随时间的推移，PE上P1升，SRAS曲线一直

向左移动，直到达到

长期均衡点C。Y与失业率回到起始水平P3P2CY2BA事件：加拿大经济繁荣影响NX，AD曲线AD曲线向右移动短期均衡在点B。P与Y增加，失业率降低（2）AnAdverseShiftinAggregateSupplyAdecreaseinoneofthedeterminantsofaggregatesupplyshiftsthecurvetotheleft:Outputfallsbelowthenaturalrateofemployment.Unemploymentrises.Thepricelevelrises.（2）总供给的不利移动总供给决定因素中任何一种降低都使总供给曲线向左移动:产量下降到自然就业率水平以下。失业率上升。物价水平上涨。Fi垦gur坦e1停0翻A雾nAd形ver青se斤S生hi松ft中i辱nA净底ggr创e扰gat蚊eS烟棋upp壳ly句Qua烫nt惹it薪yo观f碎Out者pu杨tPri米ce惰Lev拖el荐Aggregate

demand3.

.

.

.

andthe

pricelevel

to

rise.2.

.

.

.

causes

output

to

fall

.

.

.1.

An

adverse

shift

in

the

short-runaggregate-supplycurve...Short-runaggregatesupply,

ASLong-runaggregatesupplyYAPAS2B0

Y2P2图10丽.抗总艺供给吊的不倚利移拾动产量物价水平总需求2....引起产量减少...1.短期总供给曲线的不利移动……短期总供给AS长期总供给APAS2B3....以及物价水平上升。0

Y2

YP2TheEffectsofaShiftinAggregateSupply（1）StagflationAdverseshiftsinaggregatesupplycausestagflation—aperiodofrecessionandinflation.Outputfallsandpricesrise.Policymakerswhocaninfluenceaggregatedemandcannotoffsetbothoftheseadverseeffectssimultaneously.总供给移动的影响（1）滞胀总供给的不利移动会引起滞胀—衰退和通货膨胀并存的时期。产量减少而物价上升。那些能影响总需求的决策者不能同时抵消这两种不利的影响。（2）PolicyResponsestoRecessionPolicymakersmayrespondtoarecessioninoneofthefollowingways:Donothingandwaitforpricesandwagestoadjust.Takeactiontoincreaseaggregatedemandbyusingmonetaryandfiscalpolicy.总供给移动的影响（2）对付衰退的政策政策制定者可以用下列手段之一来对付衰退:什么也不做，等待价格和工资调整。利用货币和财政政策增加总需求。Fi吸gur民e1览1励A笼c模co略mm宏oda买ti颤ng侄鼻anA岸待dve呀r晚seS只h菊if背ti丹n棕完

Agg铜r忘ega尚te折S膨u毕ppl朵yQua敬nt缠it导yo撇f历Out翻pu球tNat底ur密al济r孩at猜eofo喂u竟t偶put雁Pri钓ce艘Lev僻el按0Short-runaggregatesupply,

ASLong-runaggregatesupplyAAS23.

.

.

.

whichcauses

theprice

levelto

risefurther

.

.

.4.

.

.

.

but

keeps

outputat

its

naturalrate.2.

.

.

.

policymakers

canaccommodate

the

shiftby

expanding

aggregatedemand

.

.

.1.

When

short-run

aggregatesupply

falls

.

.

.AD2Aggregatedemand,

ADCP3P2P图11佣.倚抵触消总遣供给虚的不片利移异动产量自然产郑量率宫物价水平0短期总供给AS长期总供给ADAAS23....这引起物价水平进一步上升……4....但产